Mining Bees & Ground Nesting Wasps
Mining bees, or digger bees, (familys Andrenidae & Anthophoridae) nest in burrows in the ground. Unlike the honey bee, mining bees are “solitary” bees. They do not form long-lived colonies, nor do they live inside a single, well-defended nest controlled by one queen bee. Instead, each mining bee female usually digs her own individual burrow to rear her own young. Large numbers of these bees may nest near one another if soil conditions are suitable.
Mining bees are not aggressive and seldom, if ever, sting. The presence of numerous bees flying close to the ground, however, may constitute a nuisance for some people. Sometimes large numbers of males will fly about the same spot for several days in a mating display.
Mining bees range in size from about the size of honey bees to much smaller. The larger bees are furry and usually darker in color than honey bees. Some are brightly striped, while others are a shiny metallic green. Mining bee burrows may be located wherever there is exposed soil and good drainage. They are frequently found nesting in banks, such as along road cuts or any type of excavation, but may also be in level ground as well. The holes are about 6 mm (1/4 inch) or less in diameter. They are sometimes surrounded by a small mound of soil that the bee has brought up to the surface. Burrow structure varies according to species, but often there is a vertical tunnel with smaller side tunnels that terminate in a single cell.
The female mining bee stocks each cell with pollen and nectar she collects from flowers and then deposits an egg on the food mass. The larva hatches and consumes the stored pollen and nectar. When mature, it becomes a pupa, or resting stage, and finally becomes an adult bee. The adult bees overwinter below ground in the burrow site. During the next spring or early summer the adults emerge, mate, and the females begin burrow excavation. Mining bee populations can fluctuate dramatically from one season to the next.
Ground Nesting Wasps:
Many species of wasps are also solitary and nest in the ground. They have a life cycle similar to that of the mining bees. After preparing a burrow, the female wasp stocks it with provisions (which consist of insect or spider prey rather than pollen and nectar), lays one or more eggs in it, seals it and departs. Some species don’t permanently seal the nest, but instead return repeatedly with additional prey as their larvae grow. These wasps range in size from extremely small forms to the large, fearsome looking “cicada killers.”
Cicada Killers (Specius speciousus): Cicada killers resemble large yellowjackets. They are mostly black with pale yellow markings on the abdomen, and about 5 cm (2 inches) long. Despite their appearance, these insects are inoffensive and usually will not bother people even when provoked. Their sting is meant for paralyzing their prey and normally does not cause a reaction in humans. They are considered beneficial because they reduce cicada populations. However, they may cause lawn damage if there are large numbers of them nesting in close proximity to each other.
Another group of ground nesting wasps are the Scoliid (family: Scoliidae) or Tiphiid (family: Tiphiidae) wasps. Scoliid wasps are about 16 mm (5/8 inch) long and blue-black, with blackish-purple wings. They have a yellow stripe on each side of the abdomen. Their bodies are fairly hairy and the back part of the abdomen is covered with reddish hairs. Tiphiid wasps are black and somewhat hairy with short, spiny legs. Both wasps are generally seen flying over the lawn during the day, leaving in early evening. Scoliids and Tiphiids are beneficial wasps in that they parasitize grub populations. They are not aggressive and generally do not attack humans. Adults are often seen on golden rod flowers in the late summer.
It must be stressed that mining bees are extremely beneficial insects, of considerable importance in the pollination of many different types of plants. Their burrowing does not harm vegetation and may actually be of service in aerating the soil. Furthermore, the activity of these species is extremely brief, with adult bees flying for only two to four weeks. In some instances, the bees observed are males flying about their territory; males cannot sting, nor do they make burrows. We do not recommend using insecticides to control mining bees and ground nesting wasps; it is virtually impossible to eliminate the population in a single season.